[island911]

Yeah, GK, I get that; why use air when coiled steel has a phenomenally good history? Seems reasonable.

Well, there is a compelling reason; or two. First, the obvious - Porsche clearly wanted the Cayenne to perform exceedingly well regardless of the road (or no road) conditions. Ground clearance vs aerodynamics at speed. The Air-sprung Cayenne will sling closer to the road (ala 959) at speed - which it has PLENTY. Off-road, the user can push it up high for ease of clearing rocks and rut-mounds.

Now for what is not so obvious - damper control. The PASM system (Porsche Active Stability Management - aka, air suspension) also comes with lightning-fast control over the shocks. The computer is sensing and processing massive telemetry and load data against user input (steering angle, gas, brake...) and adjusting each damper force on the fly. The result is impressive. The relatively top-heavy, heavy Cayenne has handling manners better than say a super low CG car (911). While cornering seems strangely better than it should be, Braking is where the system really shines. Ya know how threshold braking a 911 takes some skill ... the timing of loading up the front suspension... getting front tires to dig-in w/o locking up while the car's inertia transfers to the front suspension? Yeah, you don't have to wait much/any for that on the PASM system. Those front 'shocks'(dampers) lock-down quickly for a stunningly quick deceleration. --That is, full weight transfer to where the rubber meets the road happen now!

If you choose steel springs you trade all of that performance for piece of mind, on the system reliability.